Targeted cancer therapies that can selectively kill cancer cells without harming other cells in the body would represent a major improvement in the clinical treatment of cancer. It would be highly desirable to develop a strategy to directly target cancer cells with chemotherapeutic agents in cancer treatment regimens. This could lead to reduction or elimination of toxic side effects, more efficient delivery of the drug to the targeted site, and reduction in dosage of the administered drug and a resulting decrease in toxicity to healthy cells and in the cost of the chemotherapeutic regimen. Reports of targeting chemotherapeutic drugs using antibodies have appeared in the literature since 1958. Targeting drugs by conjugation to antibodies for selective delivery to cancer cells has had limited success due to the large size of antibodies (MW=125-150 kilodaltons or KD) and thus their relative inability to penetrate solid tumors. An alternative strategy comprises the use of smaller targeting ligands and peptides, which recognize specific receptors unique to or overexpressed on tumor cells, as the targeting vector. Such constructs have molecular weights of 2-6 KD, which allow ready penetration throughout solid tumors.
Increased cell proliferation and growth is a trademark of cancer. The increase in cellular proliferation is associated with high turnover of cell cholesterol. Cells requiring cholesterol for membrane synthesis and growth may acquire cholesterol by receptor mediated endocytosis of plasma low density lipoproteins (LDL), the major transporter of cholesterol in the blood, or by de novo synthesis. LDL is taken up into cells by a receptor known as the LDL receptor (LDLR); the LDL along with the receptor is endocytosed and transported into the cells in endosomes. The endosomes become acidified and this releases the LDL receptor from the LDL; the LDL receptor recycles to the surface where it can participate in additional uptake of LDL particles. There is a body of evidence that suggests that tumors in a variety of tissues have a high requirement for LDL to the extent that plasma LDLs are depleted. The increased import of LDL into cancerous cells is thought to be due to elevated LDL receptors (LDLR) in these tumors. Some tumors known to express high numbers of LDLRs include some forms of leukemia, lung tumors, colorectal tumors and ovarian cancer. In vivo studies showed that LDLRs do appear in brain malignancies. Leppala et al used PET imaging, and demonstrated that 99mTc_LDL localizes in human brain tumors in vivo but not in normal brain.
This suggests that the LDL receptor is a potential unique molecular target in GBM and other malignancies for the delivery of anti-tumor drugs via LDL particles. A test of this possibility was undertaken by Maranhão and coworkers. A protein-free microemulsion (LDE) with a lipid composition resembling that of low-density lipoprotein (LDL) was used in metabolic studies in rats to compare LDE with the native lipoprotein. Incubation studies also showed that LDE incorporates a variety of apolipoproteins, including apo E, a ligand for recognition of lipoproteins by specific receptors.
Lipophilic Derivatives of Cancer Chemotherapeutic Agents:
Arbor Therapeutics has developed unique lipophilic derivatives of the cancer chemotherapeutic agent which have high stability in normal systemic circulation and retention in the lipid core of the LDL particles but readily release the active chemotherapeutic agent in the acidic environment of the endosome. See U.S. Pat. No. 8,440,714, the disclosure of which is incorporated herein in its entirety.
In another embodiment, there is provided a active chemotherapeutic compounds of the formula 3a or 3b:
wherein: R1 is hydrogen, C1-C4 alkyl or C5-C22 alkyl; R2 is C5-C22 alkyl; Y is selected from O, NR′ or S wherein R′ is hydrogen or C1-C6 alkyl; Z is selected from O or S; Q is O or S; and T is O or S. In one aspect of the compound, R1 is hydrogen or C1-C4 alkyl; R2 is C5-C22 alkyl; Y is O or S; Z is O; Q is O; and T is O. The activated compound of the formula 3a or 3b may be used to prepare the acid labile lipophilic conjugate when the activated compound is condensed with a hydroxyl bearing cancer chemotherapeutic agent (HBCCA). As defined herein, the HBCCA is represented generically with the residue or group “R” in the formulae 1, 1a, 1b, 1.1, 2 and 2a, for example, and where the HBCCA is not coupled to form the acid labile, lipophilic molecular conjugates, then the HBCCA may also be generically represented as having the formula “R—OH” since the HBCCA may be functionalized by one or more hydroxyl (—OH) groups.
In one embodiment, there is provided an acid labile lipophilic molecular conjugate (ALLMC) of the formula 1, 1.1 or formula 2:
wherein: R is a hydroxyl bearing cancer chemotherapeutic agent; for formula 1 or 1.1 R1 is hydrogen, C1-C4 alkyl or C5-C22 alkyl; R2 is C5-C22 alkyl; Y is selected from O, NR′ or S wherein R′ is hydrogen or C1-C6 alkyl; Z is O or S; Q is O or S; and T is O or S; for formula 2: R2 is a C1-C22 alkyl; T is O or S; and X is hydrogen or a leaving group selected from the group consisting of mesylates, sulfonates and halogen (Cl, Br and I); and their isolated enantiomers, diastereoisomers or mixtures thereof, or a pharmaceutically acceptable salt thereof. The compound 1.1 includes the pure syn isomer, the pure anti isomer and mixtures of syn- and anti-isomers, and their diastereomers.
In another embodiment, there is provided the above acid labile lipophilic molecular conjugate of the formula 1 or 1.1 wherein: R is a hydroxyl bearing cancer chemotherapeutic agent; R1 is hydrogen, C1-C4 alkyl or C5-C22 alkyl; R2 is C5-C22 alkyl; Y is O or S; Z is O; Q is O; and T is O. In one aspect of the acid labile lipophilic molecular conjugate of the formula 2 wherein: R2 is C5-C22 alkyl; T is O; and X is hydrogen or selected from the group consisting of Cl, Br and I. In another variation, R2 is C9-C22. In another aspect of the above acid labile lipophilic molecular conjugate comprising the formula 1a, 1b or formula 2a:
wherein: R is a hydroxyl bearing cancer chemotherapeutic agent (HBCCA); for formula 1a or 1b R1 is hydrogen, C1-C4 alkyl or C5-C22 alkyl; and R2 is C5-C22 alkyl; and for formula 2a: R2 is C1-C22 alkyl; and X is hydrogen or is selected from the group consisting of Cl, Br and I. In one variation of the compound that is the carbonate (i.e., —OC(O)O—) of the formula 1a or 1b the compound is the corresponding sulfonate (i.e., —OS(O)O—) of the formula 1a wherein the carbonate group is replaced by a sulfonate group. The compound 1b includes the pure syn isomer, the pure anti isomer and mixtures of syn and anti isomers, and their diastereomers.
In another variation of the compound of the formula 1, 2, 1a and 2a, R1 is hydrogen or C1-C4 alkyl or C5-C22 alkyl, and R2 is the carbon residue of an unsaturated fatty acid, such as the carbon residue selected from the group consisting of the C19 residue of eicosenoic acid (including the cis isomer, trans isomer and mixtures of isomers), C17 residue of oleic acid and the C17 residue of elaidic acid. As used herein, the “carbon residue” (e.g., C17 residue, C19 residue etc . . . ) of the fatty acid means the carbon chain of the fatty acids excluding the carboxyl carbon.
In another aspect of the above acid labile lipophilic molecular conjugate, the hydroxyl bearing cancer chemotherapeutic agent is selected from the group consisting of taxanes, abeo-taxanes, camptothecins, epothilones, cucurbitacins, quassinoids, anthracyclines, and their analogs and derivatives. In another aspect of the above acid labile lipophilic molecular conjugate, the hydroxyl bearing cancer chemotherapeutic agent is selected from the group consisting of aclarubicin, camptothecin, masoprocol, paclitaxel, pentostatin, amrubicin, cladribine, cytarabine, docetaxel, gemcitabine, elliptinium acetate, epirubicin, etoposide, formestane, fulvestrant, idarubicin, pirarubicin, topotecan, valrubicin and vinblastine.
In one embodiment, there is provided an acid labile lipophilic molecular conjugate (ALLMC) of the formula 1, 1.1 or formula 2:
wherein: R is a hydroxyl bearing cancer chemotherapeutic agent; for formula 1 or 1.1 R1 is hydrogen, C1-C4 alkyl or C5-C22 alkyl; R2 is C5-C22 alkyl; Y is selected from O, NR′ or S wherein R′ is hydrogen or C1-C6 alkyl; Z is O or S; Q is O or S; and T is O or S; for formula 2: R2 is a C1-C22 alkyl; T is O or S; and X is hydrogen or a leaving group selected from the group consisting of mesylates, sulfonates and halogen (Cl, Br and I); and their isolated enantiomers, diastereoisomers or mixtures thereof, or a pharmaceutically acceptable salt thereof. The compound 1.1 includes the pure syn isomer, the pure anti isomer and mixtures of syn- and anti-isomers, and their diastereomers.
In another embodiment, there is provided the above acid labile lipophilic molecular conjugate of the formula 1 or 1.1 wherein: R is a hydroxyl bearing cancer chemotherapeutic agent; R1 is hydrogen, C1-C4 alkyl or C5-C22 alkyl; R2 is C5-C22 alkyl; Y is O or S; Z is O; Q is O; and T is O. In one aspect of the acid labile lipophilic molecular conjugate of the formula 2 wherein: R2 is C5-C22 alkyl; T is O; and X is hydrogen or selected from the group consisting of Cl, Br and I. In another variation, R2 is C9-C22. In another aspect of the above acid labile lipophilic molecular conjugate comprising the formula 1a, 1b or formula 2a:
wherein: R is a hydroxyl bearing cancer chemotherapeutic agent (HBCCA); for formula 1a or 1b R1 is hydrogen, C1-C4 alkyl or C5-C22 alkyl; and R2 is C5-C22 alkyl; and for formula 2a: R2 is C1-C22 alkyl; and X is hydrogen or is selected from the group consisting of Cl, Br and I. In one variation of the compound that is the carbonate (i.e., —OC(O)O—) of the formula 1a or 1b the compound is the corresponding sulfonate (i.e., —OS(O)O—) of the formula 1a wherein the carbonate group is replaced by a sulfonate group. The compound 1b includes the pure syn isomer, the pure anti isomer and mixtures of syn and anti isomers, and their diastereomers.
In another variation of the compound of the formula 1, 2, 1a and 2a, R1 is hydrogen or C1-C4 alkyl or C5-C22 alkyl, and R2 is the carbon residue of an unsaturated fatty acid, such as the carbon residue selected from the group consisting of the C19 residue of eicosenoic acid (including the cis isomer, trans isomer and mixtures of isomers), C17 residue of oleic acid and the C17 residue of elaidic acid. As used herein, the “carbon residue” (e.g., C17 residue, C19 residue etc . . . ) of the fatty acid means the carbon chain of the fatty acids excluding the carboxyl carbon. In another aspect of the above acid labile lipophilic molecular conjugate, the hydroxyl bearing cancer chemotherapeutic agent is selected from the group consisting of taxanes, abeo-taxanes, camptothecins, epothilones, cucurbitacins, quassinoids, anthracyclines, and their analogs and derivatives. In another aspect of the above acid labile lipophilic molecular conjugate, the hydroxyl bearing cancer chemotherapeutic agent is selected from the group consisting of aclarubicin, camptothecin, masoprocol, paclitaxel, pentostatin, amrubicin, cladribine, cytarabine, docetaxel, gemcitabine, elliptinium acetate, epirubicin, etoposide, formestane, fulvestrant, idarubicin, pirarubicin, topotecan, valrubicin and vinblastine. In another aspect of the above acid labile lipophilic molecular conjugate, the conjugate is selected from the compounds in FIGS. 18, 19 and 20. In one variation, only one of the groups -ALL1, -ALL2, -ALL3 . . . to -ALLn is an -ALL group and the others are hydrogens. In another variation, two of the groups -ALL1, -ALL2, -ALL3 . . . to -ALLn are -ALL groups.
In another embodiment, there is provided a pharmaceutical composition comprising: a) a therapeutically effective amount of a compound of the above, in the form of a single diastereoisomer; and b) a pharmaceutically acceptable excipient. In another aspect, the pharmaceutical composition is adapted for oral administration; or as a liquid formulation adapted for parenteral administration. In another aspect, the composition is adapted for administration by a route selected from the group consisting of orally, parenterally, intraperitoneally, intravenously, intraarteriall, transdermally, intramuscularly, rectally, intranasally, liposomally, subcutaneously and intrathecally. In another embodiment, there is provided a method for the treatment of cancer in a patient comprising administering to the patient a therapeutically effective amount of a compound or composition of any of the above compound or composition, to a patient in need of such treatment. In one aspect of the method, the cancer is selected from the group consisting of leukemia, neuroblastoma, glioblastoma, cervical, colorectal, pancreatic, renal and melanoma. In another aspect of the method, the cancer is selected from the group consisting of lung, breast, prostate, ovarian and head and neck. In another aspect of the method, the method provides at least a 10%, 20%, 30%, 40%, or at least a 50% diminished degree of resistance expressed by the cancer cells when compared with the non-conjugated hydroxyl bearing cancer chemotherapeutic agent.
In another embodiment, there is provided a method for reducing or substantially eliminating the side effects of chemotherapy associated with the administration of a cancer chemotherapeutic agent to a patient, the method comprising administering to the patient a therapeutically effective amount of an acid labile lipophilic molecular conjugate of the formula 1, 1.1 or formula 2:

wherein: R is a hydroxyl bearing cancer chemotherapeutic agent; for formula 1 or 1.1: R1 is hydrogen, C1-C4 alkyl or C5-C22 alkyl; R2 is C5-C22 alkyl; Y is selected from O, NR′ or S wherein R′ is hydrogen or C1-C6 alkyl; Z is O or S; Q is O or S; and T is O or S; for formula 2: R2 is C1-C22 alkyl; T is O or S; and X is hydrogen or a leaving group selected from the group consisting of mesylates, sulfonates and halogen (Cl, Br and I); and their isolated enantiomers, diastereoisomers or mixtures thereof. The compound 1.1 includes the pure syn isomer, the pure anti isomer and mixtures of syn and anti isomers, and their diastereomers. In one variation of the above, R2 is C9-C22 alkyl. In one aspect, the method provides a higher concentration of the cancer chemotherapeutic agent in a cancer cell of the patient. In another aspect, the method delivers a higher concentration of the cancer chemotherapeutic agent in the cancer cell, when compared to the administration of a non-conjugated cancer chemotherapeutic agent to the patient, by at least 5%, 10%, 20%, 30%, 40% or at least 50%.
In another embodiment, there is provided a compound of the formula 3a or 3b:

wherein: R1 is hydrogen, C1-C4 alkyl or C5-C22 alkyl; R2 is C5-C22 alkyl; Y is selected from O, NR′ or S wherein R′ is hydrogen or C1-C6 alkyl; Z is selected from O or S; Q is O or S; and T is O or S. In one aspect of the compound, R1 is hydrogen or C1-C4 alkyl; R2 is C5-C22 alkyl; Y is O or S; Z is O; Q is O; and T is O. The activated compound of the formula 3a or 3b may be used to prepare the acid labile lipophilic conjugate when the activated compound is condensed with a hydroxyl bearing cancer chemotherapeutic agent (HBCCA). As defined herein, the HBCCA is represented generically with the residue or group “R” in the formulae 1, 1a, 1b, 1.1, 2 and 2a, for example, and where the HBCCA is not coupled to form the acid labile, lipophilic molecular conjugates, then the HBCCA may also be represented as having the formula “R—OH” since the HBCCA may be functionalized by one or more hydroxyl (—OH) groups.
Similarly, the acid labile lipophilic group (i.e., the “-ALL” group of the activated compound) that may be condensed with a HBCCA to form the acid labile, lipophilic molecular conjugate generically represented as “R—O-ALL.” Accordingly, where more than one -ALL group is condensed or conjugated with a HBCCA group, then each -ALL group may be independently designated as -ALL1, -ALL2, -ALL3 . . . to -ALLn where n is the number of available hydroxyl groups on the cancer chemotherapeutic agent that may be conjugated or couple with an -ALL group. As exemplified for the compound of formulae 1 and 2, for example, the HBCCA and the -ALL groups as designated, are shown below.

An example of an acid labile, lipophilic molecular conjugate (ALLMC), where the HBCCA group is paclitaxel having two -ALL groups, is depicted below:
